Fig. 5.

Aerenchyma at three positions along adventitious roots of rice, following transfer into aerated or stagnant deoxygenated agar nutrient solutions (A). Cross-sections at 15 mm below the root–shoot junction – termed ‘basal region’ (B), at 20 mm behind the root apex at the initiation of treatment – termed ‘intermediate region’ (C), and 20 mm behind the root apex at each time point – termed ‘apical region’ (D), were taken by hand with a razor blade and photographed under a microscope and the proportion of aerenchyma was determined. Plants were raised for 3–4 weeks in aerated nutrient solution, prior to transfer to stagnant deoxygenated agar nutrient solution for 0, 6, 12, 24, 48 or 120 h. Values are means ± s.e. Sample number and length of roots used in these measurements are given in Table 1. Different lower-case letters denote significant differences among root length classes and treatments (P < 0·05, one-way ANOVA and then Scheffé's test for multiple comparison).